U.S. patent application number 13/706065 was filed with the patent office on 2014-06-05 for roofing membranes and methods for constructing.
The applicant listed for this patent is JOHNS MANVILLE. Invention is credited to Lichih R. Peng.
Application Number | 20140150960 13/706065 |
Document ID | / |
Family ID | 50824272 |
Filed Date | 2014-06-05 |
United States Patent
Application |
20140150960 |
Kind Code |
A1 |
Peng; Lichih R. |
June 5, 2014 |
ROOFING MEMBRANES AND METHODS FOR CONSTRUCTING
Abstract
Embodiments of the invention provide improved roofing membranes
and methods and systems involving the same. According to one
embodiment, a roofing membrane laminate is provided. The roofing
membrane laminate includes a first membrane layer that includes a
thermoplastic polyolefin material and a second membrane layer
positioned atop the first membrane layer and bonded thereto. The
second membrane layer includes a thermoplastic polyolefin material
and an acrylate additive blended with the thermoplastic polyolefin
material. The acrylate additive is blended with the thermoplastic
polyolefin material while both materials are resins and is added so
as to comprise 10% by weight or less of the blended resins. The
acrylate additive includes an ethylene backbone chain and an
acrylate bonded with the ethylene backbone chain.
Inventors: |
Peng; Lichih R.; (Littleton,
CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JOHNS MANVILLE |
Denver |
CO |
US |
|
|
Family ID: |
50824272 |
Appl. No.: |
13/706065 |
Filed: |
December 5, 2012 |
Current U.S.
Class: |
156/244.11 ;
264/176.1; 428/516; 525/201; 525/207; 525/221 |
Current CPC
Class: |
E04D 5/06 20130101; E04D
5/10 20130101; B32B 27/32 20130101; B32B 2419/06 20130101; Y10T
428/31913 20150401; B32B 27/00 20130101 |
Class at
Publication: |
156/244.11 ;
525/221; 525/207; 525/201; 264/176.1; 428/516 |
International
Class: |
C09D 5/00 20060101
C09D005/00; E04D 5/10 20060101 E04D005/10 |
Claims
1. A roofing membrane laminate having improved heat reflective
properties, the roofing membrane laminate comprising: a first
membrane layer, the first membrane layer comprising thermoplastic
polyolefin; and a second membrane layer positioned atop the first
membrane layer and bonded thereto, wherein the second membrane
layer comprises: thermoplastic polyolefin; and a copolymer additive
blended with the thermoplastic polyolefin, the copolymer additive
being blended with the thermoplastic polyolefin while both
materials are a resin so as to comprise 10% by weight or less of
the blended resin, wherein the copolymer additive includes: an
ethylene backbone chain bonded with the thermoplastic polyolefin;
and an acrylate bonded with the ethylene backbone chain.
2. The roofing membrane laminate of claim 1, wherein the acrylate
is included or incorporated within the ethylene backbone chain.
3. The roofing membrane laminate of claim 2, wherein the acrylate
is further bonded or grafted with the ethylene backbone chain as a
pendant group.
4. The roofing membrane laminate of claim 1, wherein the acrylate
is bonded or grafted with the ethylene backbone chain as a pendant
group.
5. The roofing membrane laminate of claim 1, wherein the copolymer
additive is blended with the thermoplastic polyolefin so as to
comprise 5% by weight or less of the blended resin.
6. The roofing membrane laminate of claim 1, wherein the copolymer
additive is blended with the thermoplastic polyolefin so as to
comprise 3% by weight or less of the blended resin.
7. The roofing membrane laminate of claim 1, wherein the copolymer
additive further comprises maleic anhydride bonded with the
ethylene backbone chain.
8. The roofing membrane laminate of claim 7, wherein a fire
retardant is bonded with the maleic anhydride pendant group.
9. The roofing membrane laminate of claim 1, further comprising a
third membrane layer, wherein the third membrane layer comprises
thermoplastic polyolefin, and wherein the first and second membrane
layers are positioned atop and bonded with the third membrane
layer.
10. A roofing membrane comprising: a thermoplastic polyolefin
material; and an acrylate additive blended with the thermoplastic
polyolefin material, the acrylate additive being blended with the
thermoplastic polyolefin material while both materials are in a
resin form such that the acrylate additive comprises 10% by weight
or less of the blended resins.
11. The roofing membrane of claim 10, wherein the thermoplastic
polyolefin material comprises polyethylene or polypropylene or a
combination thereof.
12. The roofing membrane of claim 10, wherein the acrylate additive
comprises: an ethylene chain; and an acrylate bonded with the
ethylene chain.
13. The roofing membrane of claim 10, wherein the acrylate additive
is blended with the thermoplastic polyolefin material so as to
comprise 5% by weight or less of the blended resins.
14. The roofing membrane of claim 12, wherein the acrylate additive
further comprises a maleic anhydride bonded with the ethylene
chain.
15. The roofing membrane of claim 14, wherein the maleic anhydride
is bonded with the ethylene chain so as to comprise between about
2-5% by weight of the compound chain.
16. The roofing membrane of claim 14, wherein a fire retardant is
bonded with the maleic anhydride.
17. The roofing membrane of claim 16, wherein the fire retardant
comprises magnesium hydroxide.
18. The roofing membrane of claim 10, wherein the acrylate additive
is disposed toward a surface of the roofing membrane so as to form
a polyacrylate coating, layer, or finish on the surface of the
roofing membrane.
19. A method of making a roofing membrane comprising: providing a
thermoplastic polyolefin material; blending an acrylate additive
with the thermoplastic polyolefin material so that the acrylate
additive comprises 10% by weight or less of the blended material,
the acrylate additive comprising: an ethylene chain; and an
acrylate group bonded with the ethylene chain; and forming the
blended material into a substantially flat sheet.
20. The method of claim 19, wherein the method further comprises
blending the acrylate additive with the thermoplastic polyolefin
material so that the acrylate additive comprise 5% by weight or
less of the blended material.
21. The method of claim 19, wherein the acrylate additive further
comprises a maleic anhydride bonded with the ethylene chain, and
wherein the method further comprises: blending a fire retardant
with the thermoplastic material, wherein the fire retardant bonds
with the maleic anhydride.
22. The method of claim 19, wherein forming the blended material
into a substantially flat sheet comprises extruding the blended
material through a die, wherein the acrylate additive migrates
toward a surface of the blended material so that the roofing
membrane comprises a polyacrylate coating, layer, or finish on the
surface.
23. The method of claim 19, wherein the method further comprises
coupling the roofing membrane with a roof surface.
24. The method of claim 23, wherein the method further comprises
overlaying a portion of the roofing membrane with an additional
roofing membrane and heat welding the two roofing membranes
together.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates generally to roofing membranes. More
specifically the invention relates to roofing membranes having one
or more additives that enhance properties of the roofing
membrane.
[0002] Roofing membranes are commonly used for roofing systems of
building and structures. Roofing membranes are often applied to the
building or structure's roof to prevent leaks and/or to provide
aesthetic appeal. Roofing membranes are commonly made of various
synthetic rubber materials, modified bitumen, or thermoplastic
materials.
[0003] A common type of roofing membrane is a thermoplastic
polyolefin or TPO membrane. These membranes are often white, but
may be made in various other colors or shades, such as grey, black,
and the like. White TPO roofing membranes are often used to provide
a pleasing appeal to the building and/or to reflect radiation and
thereby minimize heat island effects. TPO roofing membranes are
prone to weathering or degradation overtime, however, and may begin
to collect dust, soot, and other debris. This material is normally
easily removed from new TPO membranes, but may be more difficult to
remove over time due to the effects or weathering. As such, the
dust, soot, and other debris may remain on the surface of the TPO
membrane affecting its overall appearance and functionality. For
example, the TPO membrane may appear dull white or brownish-grey.
The thermal conductivity and/or heat reflectance of the TPO
membrane may also increase due to the darker appearance of the
membrane.
BRIEF SUMMARY OF THE INVENTION
[0004] Embodiments of the invention provide roofing membranes
having improved properties over conventional membranes. For
example, the roofing membranes described herein may exhibit
increased resistance to weather or degradation, which may affect
the membranes appearance and/or functional ability over an extended
period of time. The membranes may be less prone to retaining dust,
soot, or other debris that contacts the membranes' surfaces. The
membranes may also exhibit enhanced weldability, strength, fire
resistance, and/or other properties.
[0005] According to one aspect, a roofing membrane laminate having
improved heat reflective properties is provided. The roofing
membrane laminate may include a first membrane layer that includes
a thermoplastic polyolefin material and a second membrane layer
positioned atop the first membrane layer and bonded thereto. The
second membrane layer may include a thermoplastic polyolefin
material and a copolymer or acrylate additive blended with the
thermoplastic polyolefin material. The copolymer additive may be
blended with the thermoplastic polyolefin material while both
materials are in a resin state or form and may be added so as to
comprise 10% by weight or less of the blended resins. The copolymer
additive may include an ethylene backbone chain that is able to
bond with the thermoplastic polyolefin material and an acrylate
bonded with the ethylene backbone chain.
[0006] According to some embodiments, the acrylate may be included
or incorporated within the ethylene backbone chain. In other
embodiments, the acrylate may also be grafted or bonded with the
ethylene backbone chain as a pendant group. In yet other
embodiments, the acrylate may be bonded with the ethylene backbone
chain as a pendant group without including any of the acrylate
within the backbone chain.
[0007] In some embodiments, the copolymer additive may be blended
with the thermoplastic polyolefin material so as to comprise 5% by
weight or less of the blended resins, or 3% by weight or less of
the blended resins. The copolymer additive may also include a
maleic anhydride bonded with the ethylene backbone chain. A fire
retardant may be bonded with the maleic anhydride pendant
group.
[0008] In some embodiments, the roofing membrane laminate may also
include a third membrane layer. The third membrane layer may also
include a thermoplastic polyolefin material and the first and
second membrane layers may be positioned atop and bonded with the
third membrane layer.
[0009] According to another aspect, a roofing membrane is provided.
The roofing membrane may include a thermoplastic polyolefin
material and an acrylate additive blended therewith while both
materials are resins so as to comprise 10% by weight or less of the
blended resins. In some embodiments, the acrylate additive may be
blended with the thermoplastic material so as to comprise 5% by
weight or less of the blended resins, or 3% by weight or less of
the blended resins. The thermoplastic polyolefin material may
include polyethylene, polypropylene, or a combination thereof
according to some embodiments. The acrylate additive may include an
ethylene chain and an acrylate group bonded with the ethylene
chain.
[0010] The acrylate additive may also include a maleic anhydride
bonded with the ethylene chain. A fire retardant, such as magnesium
hydroxide, aluminum tri-hydrate, and the like may be bonded with
the maleic anhydride. The acrylate additive may be disposed toward
a major surface of the roofing membrane so as to form a
polyacrylate coating, layer, or finish on the major surface of the
roofing membrane.
[0011] According to another aspect, a method of making a roofing
membrane is provided. The method may include providing a
thermoplastic polyolefin material and blending an acrylate additive
with the thermoplastic polyolefin material so that the acrylate
additive comprises 10% by weight or less of the blended material,
5% by weight or less of the blended material, 3% by weight or less
of the blended material, and the like. The acrylate additive may
include an ethylene chain and an acrylate group bonded with the
ethylene chain.
[0012] The method may also include forming the blended material
into a substantially flat sheet, such as by extruding the blended
material through a die. In some embodiments, the acrylate additive
may migrate toward a major surface of the blended material during
extrusion so that the roofing membrane comprises a polyacrylate
coating, layer, or finish on its major surface or both major
surfaces.
[0013] The acrylate additive may also include a maleic anhydride
bonded with the ethylene chain. In such embodiments, the method may
further include blending a fire retardant with the thermoplastic
material. The fire retardant may bond with the maleic
anhydride.
[0014] The method may additionally include coupling the roofing
membrane with a roof surface. In some embodiments, a portion of the
roofing membrane may be overlaid with an additional roofing
membrane and the two membranes may be heat welded along the
overlapping portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The present invention is described in conjunction with the
appended figures:
[0016] FIG. 1 illustrates a roofing system including a plurality of
roofing membranes coupled together according to an embodiment of
the invention.
[0017] FIG. 2 illustrates the roofing system of FIG. 1 reflecting
radiation incident upon the roofing system's surface according to
an embodiment of the invention.
[0018] FIG. 3 illustrates a method of making a roofing membrane
according to an embodiment of the invention.
[0019] FIGS. 4A-C illustrate various copolymer additive
compositions according to an embodiment of the invention.
[0020] FIGS. 5A & B illustrate various roofing membrane
laminates according to an embodiment of the invention.
[0021] FIG. 6 illustrates the anion portion of acrylic acid
according to an embodiment of the invention.
[0022] In the appended figures, similar components and/or features
may have the same numerical reference label. Further, various
components of the same type may be distinguished by following the
reference label by a letter that distinguishes among the similar
components and/or features. If only the first numerical reference
label is used in the specification, the description is applicable
to any one of the similar components and/or features having the
same first numerical reference label irrespective of the letter
suffix.
DETAILED DESCRIPTION OF THE INVENTION
[0023] The ensuing description provides exemplary embodiments only,
and is not intended to limit the scope, applicability or
configuration of the disclosure. Rather, the ensuing description of
the exemplary embodiments will provide those skilled in the art
with an enabling description for implementing one or more exemplary
embodiments. It being understood that various changes may be made
in the function and arrangement of elements without departing from
the spirit and scope of the invention as set forth in the appended
claims.
[0024] The roofing membranes described herein are typically made of
thermoplastic materials. An exemplary such roofing membrane is made
of olefin or polyolefin and is commonly known by the trade name
Thermoplastic Olefin, Thermoplastic PolyOlefin, or simply TPO.
Other thermoplastic membranes include Polyvinyl Chloride (CPA/PVC),
Chlorinated Polyethylene (CPE), and the like. For convenience the
roofing membranes described herein will be referred to generally as
Thermoplastic PolyOlefin or TPO roofing membranes, although it
should be realized that the embodiments are not limited to these
specific types of membranes.
[0025] The term Thermoplastic PolyOlefin or TPO may describe
various roofing membranes configurations. For example, in one
embodiment, a TPO roofing membrane may have one or more polymers
blended with one or more fillers. The membrane may include some
combination of the following materials: polypropylene,
polyethylene, block copolymer polypropylene, rubber, plasticizers,
fiberglass, carbon fiber, fire retardants, and the like. In another
embodiment, a TPO roofing membrane may have a more pure polymer
blend without or with very few fillers. For example, the membrane
may include mainly polypropylene or polyethylene or some
combination of these polymers with little to no fillers, although
in some embodiments, these membranes may include some amount of a
filler, such as a fire retardant.
[0026] The term acrylate is also used herein. This term is commonly
understood to be the anion portion of acrylic acid as shown in FIG.
6 and may describe various compounds including: acrylic acid,
methacrylic acid, various salts and esters of acrylic and/or
methacrylic acid, and the like. It should be understood that the
term is not limited to any specific compound herein unless
explicitly claimed or described.
[0027] Embodiments of the invention provide roofing membranes
having one or more additives that improve one or more properties of
the roofing membranes. According to one embodiment, the roofing
membranes described herein exhibit less sign of wear and/or
degradation over time, thereby allowing the color and/or brightness
of the roofing membrane to remain intact even after an extended
period of time. For example, roofing membranes are often
manufactured to have a white appearance for both aesthetic and
functional purposes. The white appearance may be used to enhance
the look or appearance of a building or structure they are coupled
with, such as by providing a brilliant white roofing surface. In
addition, the roofing membranes may be used to reflect radiation or
heat, which may reduce urban heat island effects.
[0028] New roofing membranes typically have a low surface friction
coefficient, which allows the surface to remain relatively clean
and free of dust, soot, debris, and the like. For example, dust,
soot, debris, and the like easily wash away with rain or water so
that the surface remains relatively free of these materials and is
able to maintain its appearance and other functional properties.
The low surface friction also enables the surface to be easily
wiped or brushed clean of these materials.
[0029] After a period of time, however, the roofing membranes may
be prone to losing the desired appearance and/or heat reflection
properties due to a collection and retention of dust, soot, debris,
and the like on the surface. These materials may be retained due to
an increase in friction of the roofing membrane surface. The
increased friction may result from weathering or degradation of the
membrane over time, such as by acid rain, abrasion, ultraviolet or
other radiation exposure, and the like. The retained materials may
cause the surface to have a dull greyish or brownish white
appearance, which may affect the membrane's ability to reflect heat
and radiation. A decreased whiteness of the roofing membrane may
also result in the membrane absorbing more radiation and, thus,
increasing in temperature, which affects the building's solar heat
gain.
[0030] According to some embodiments, the roofing membranes
described herein may include an additive or a filler material that
reduces the effects of weathering or degradation and/or improves
the whiteness and brightness of the membrane even after an extended
period of time. The additive or filler materials may allow the
roofing membrane to retain a low surface friction coefficient so
that collected dust, soot, debris, and the like may be easily wiped
off or washed off by rain or water. The additive may include an
acrylate that is able to both bond with the roofing membrane
material and provide a low friction surface. In some embodiments,
the acrylate migrates toward the outer surfaces of the roofing
membrane during manufacture so that a substantial portion of the
acrylate is located at or near the surface of the membrane. In an
exemplary embodiment, the acrylate may be a relatively pure acrylic
acid, which may provide a smooth shiny surface on the surface of
the roofing membrane. In another embodiment, methacrylate may be
used or silicon or Teflon may be used.
[0031] The additive may be a copolymer having an ethylene component
and an acrylate component, such as a compound or backbone that
includes repeating polyethylene compounds and acrylate compounds or
an acrylate group that is bonded with a polyethylene backbone
chain. The polyethylene compound may bond with the polymer material
of the roofing membrane, such as olefin or polyolefin. The ethylene
may function to bond the acrylate with the polymer of the roofing
membrane, which bonding may otherwise be difficult. The additive
may also include one or more other compounds included within the
backbone chain or attached or grafted as pendant groups to the
ethylene backbone. For example, in one embodiment, a maleic
anhydride compound is included within the backbone chain or coupled
with the ethylene backbone. The maleic anhydride may bond with
other filler materials of the roofing membrane, such as fire
retardants, to help homogenize and diffuse the filler materials
throughout the roofing membrane and thereby improve the strength or
other properties of the roofing membrane. According to one
embodiment, the maleic anhydride is able to bond with magnesium
hydroxide, aluminum tri-hydrate, Titanium Dioxide (TiO2), talc or
other lubricants, and the like. The use of the maleic anhydride may
reduce the need for emulsifiers, such as stearic acid, to be
used.
[0032] The additive may also improve other properties of the
roofing membrane. For example, the acrylate additive may improve
the weldability of the roofing membrane by lowering the melting
temperature of the roofing membrane and thereby broaden the welding
temperature of the structure. The additive may enable the roofing
membrane to easily bond with other membranes that may or may not
include similar additives. The additive may also improve the fire
resistance of the roofing membrane by synergistically bonding with
fire retardant fillers (e.g., magnesium hydroxide, aluminum
tri-hydrate, and the like) and/or forming a protective char layer
during a fire. The formed char layer may function to shield the
membrane from further fire damage and/or limit flame spread. The
additive may likewise bond with other fillers of the roofing
membrane to enhance the overall strength of the membrane.
[0033] Having described embodiments of the invention generally,
these and other aspects of the invention will be realized with
references to the figures, which are described below. Referring now
to FIG. 1, illustrated is a roofing system 100. Roofing system 100
includes a plurality of roofing membranes 104a-c that are coupled
together, such as by heat welding, to form a single structure that
is coupled with a roof's surface. Typically a portion of adjacent
roofing membranes (e.g., 104a & b) overlap and are heat welded
along this overlapping portion. The roofing system 100 is coupled
with the roof's surface using conventional attachment means, such
as adhesives, mechanical fasteners, ballasts, and the like.
[0034] Roofing system 100 is typically made of thermoplastic
roofing membranes, such as TPO membranes, which offer several
advantages over other similar membranes. For example, TPO membranes
often last at least 20 years. Another property of TPO membranes is
the aesthetic appearance they provide, which is often brilliant
white, but may also include grey, black, and the like. White TPO
membranes are often used for their ability to reflect heat and
radiation and thereby lower or minimize the overall temperature of
the roof surface and the structure itself.
[0035] FIG. 2 illustrates a roofing system 200 including a
plurality of roofing membranes 202a-c reflecting radiation that
contacts the roofing membrane surface. Specifically, FIG. 2 shows a
plurality of rays or beams 204 contacting roofing system 200 and
reflecting off the surface of roofing system 200. The reflective
nature of roofing system 200 may be due to, or enhanced, by the
white color of roofing system 200.
[0036] Dust, soot, and other debris may collect on the surface of
such roofing systems. For example, FIG. 1 illustrates such dust,
soot, or debris 102 (hereinafter debris 102) collecting atop a
major surface of the roofing membranes 104a-c of roofing system
100. The debris 102 may collect atop roofing system 100 from dust
storms, nearby factories, periods of draught or little rain, from
nearby animals or plants, and the like. Debris 102 may alter the
aesthetic appearance of roofing system 100 by making the individual
roofing membranes 104a-c appear dullish brown/gray white. This may
hinder roofing system 100's ability to reflect radiation and/or may
cause roofing system 100 to absorb heat leading to an increase in
heat island effects.
[0037] Conventional roofing membranes may retain debris 102 making
it difficult to remove. As a result, conventional roofing systems
that include such roofing membranes may provide less aesthetic and
functional appeal due to being dullish white in appearance and
having a decreased ability to reflect radiation. The debris 102 may
be retained due to an increase in the surface friction of the
roofing membranes, which is commonly caused by weathering or
degradation of the membrane material over time, such as by acid
rain, abrasion, prolonged exposure to radiation, and the like.
[0038] The roofing membranes of the present invention are more able
to resist weathering or degradation and, thus, are able to provide
a longer lasting aesthetic look and functional appeal. According to
one embodiment, the degradation effects are resisted or minimized
by maintaining or minimizing degradation of a low surface friction
over all or a substantial portion of the life of the roofing
membrane. This allows the debris 102 on the roofing membrane
surface to be easily removed by wiping or brushing the debris off,
or by spraying the surface with water. The debris 102 may also be
naturally removed by rain water. Because the debris 102 may be
easily removed over the life of the roofing membrane, the roofing
membrane is able to maintain its brilliant white appearance over
its life. The roofing membrane also absorbs less heat over its
lifetime and is more effective at reflecting radiation and, thus,
more effective at combating urban heat island effects.
[0039] The roofing membrane is able to combat degradation by
blending an additive with the thermoplastic material, such as
thermoplastic polyolefin. According to one embodiment, an acrylate
additive is blended with a resin of the thermoplastic material,
such as by melting the two components and mixing them together with
an auger. The blended resin may be subsequently cooled and/or
extruded to form a roofing membrane that includes the additive. The
acrylate additive may be blended with the thermoplastic material so
that the additive comprises 10% by weight or less of the blended
resin. In another embodiment, the acrylate additive is blended with
the thermoplastic material to comprise 5% by weight or less of the
blended resin. In another embodiment, the acrylate additive is
blended with the thermoplastic material to comprise 3% by weight or
less of the blended resin. If more than 10% by weight of the
acrylate additive is used, the roofing membrane may not properly
bond with an adjacent membrane. Similarly, if less than 1 or 2% by
weight of the acrylate additive is used, the low surface friction
may not be maintained and/or the roofing membrane may be prone to
weathering and degradation.
[0040] As shown in FIGS. 4A-C, the acrylate additive may be a
copolymer that includes a combination of polyethylene and an
acrylate. The acrylate is typically an anion portion of acrylic
acid as shown in FIG. 6. The acrylate may include acrylic acid,
methacrylic acid, various salts and esters of acrylic and/or
methacrylic acid, and the like, or any combination thereof. As
shown in FIG. 4A, in one embodiment, the acrylate may be grafted or
included within a polyethylene backbone to form a compound chain.
The compound chain may include any number of polyethylene units and
acrylate units. For example, in one embodiment, the chain includes
multiple polyethylene units and few acrylate units. Alternatively,
the chain may include multiple acrylate units and few polyethylene
units so that the polyethylene is essentially grafted or included
within an acrylate backbone. In other embodiments, the difference
in the number of polyethylene units and acrylate units may not be
that significant. FIG. 4A illustrates an acrylic acid included
within the polyethylene chain, although it should be realized that
the embodiments described herein are not limited to acrylic acid
and that any acrylate may be used, or multiple acrylates may be
used.
[0041] As shown in FIG. 4B, in some embodiments, the acrylate may
be included as a pendant group bonded with the polyethylene
backbone. In some embodiments, the R groups may include CH.sub.3,
C.sub.2H.sub.5, C.sub.4H.sub.9, and the like (i.e., methyl, ethyl,
butyl, and the like). In some embodiments, a butyl group may be
used for increased compatibility with TPO material. Acrylic acid is
again illustrated as the pendant group although any acrylate may be
used. As shown in FIG. 4C, the compound chain may include some
combination of acrylate pendant groups bonded with the polyethylene
backbone and acrylate units included within the polyethylene
backbone. As described previously, the compounds of FIGS. 4B and 4C
may include any number of polyethylene and acrylate units or
pendant groups. The ethylene may bond with the polymer material of
the roofing membrane, such as by bonding with the polyolefin. The
ethylene may likewise couple the acrylate with the polymer
material. Such coupling is normally difficult due to the polarity
of the acrylate. In this manner, the ethylene may function as a
bridge between the polyolefin and the acrylate.
[0042] In some embodiments, the acrylate may migrate toward a major
surface, or surfaces, of the roofing membrane so as to provide a
polyacrylate layer, coating, or finish at or near the major
surface. This layer, coating, or finish may reduce the surface
friction of the roofing membrane and/or improve resistance to
weathering or other forms of degradation. The migration of the
acrylate toward the roofing membrane's major surface may be
increased during manufacturing of the roofing membrane, such as by
extruding the membrane through a die or by using an agent that
effects such migration. The migration may occur as a result of the
polarity of the acrylate units. After migration, a substantial
portion of the acrylate may be at or near the roofing membrane's
surface to provide the polyacrylate layer, coating, or finish.
[0043] The acrylate additive may also improve the weldability
and/or strength of the roofing membrane. For example, the acrylate
may lower the melting point of the roofing membrane and thereby
broaden the heat welding window. As a result, heat welding may be
initiated earlier in the welding process. Further, the ethylene
units or chain of the additive may improve the weld strength by
bonding with the polyolefin material (e.g., polyethylene,
polypropylene, and the like) of an adjacent roofing membrane. The
ethylene units or chain may improve the weld strength even when an
adjacent roofing membrane does not include an acrylate
additive.
[0044] According to some embodiments, the acrylate additive may
also include one or more maleic anhydride units or pendant groups
included within or bonded to the compound chain. For example, FIG.
4C further illustrates a maleic anhydride being included within the
compound chain and/or being included as a pendant group. The
compound chain may include multiple units of the maleic anhydride
within the compound chain or coupled thereto as pendant groups. The
maleic anhydride may improve the overall strength of the roofing
membrane and/or improve other roofing membrane properties by
bonding with various filler materials of the roofing membrane. For
example, TPO roofing membranes often include various filler
materials such as fire retardants. The maleic anhydride can
chemically bond to these filler materials to more fully strengthen
the roofing membrane. Because the maleic anhydride is included
within or bonded to the compound chain, the maleic anhydride is
able to homogenize and diffuse and lock the filler materials within
the TPO material, which otherwise may be difficult. Stated
differently, the maleic anhydride may function as a bridge between
the TPO and filler materials. According to one embodiment, the
maleic anhydride may be bonded or grafted with the ethylene chain
so as to comprise between about 2-5% by weight of the compound
chain.
[0045] In a specific example, the maleic anhydride may bond with a
fire retardant material, which may otherwise not bond with the
roofing membrane's polymer material. For example, magnesium
hydroxide is a specific type of fire retardant that is used in some
TPO membranes. Bonding between the magnesium hydroxide and the
polyolefin is generally difficult due to the polarity of the
magnesium hydroxide. As such, magnesium hydroxide is typically
treated with an acid, such as stearic acid, to enhance the bonding
between the polyolefin and the magnesium hydroxide. However, the
amount of stearic acid that is used is limited, which usually
results in an amount of untreated magnesium hydroxide being mixed
with the polyolefin. The maleic anhydride of the additive is able
to bond with the magnesium hydroxide, thereby eliminating or
reducing the amount of stearic acid that needs to be used. Further,
the ethylene chain is able to bond with the polyolefin, which
effectively locks the magnesium hydroxide within the TPO roofing
membrane.
[0046] The acrylate of the copolymer additive may also function to
resist or retard a fire. For example, the acrylate bonded with the
TPO filler materials (e.g., the flame retardant, mineral fillers,
and the like) can form a char, or cause formation of char, upon
burning or application of a flame. The formed char may form a
protective layer that helps insulate the TPO membrane from further
fire damage, such as by limiting or slowing down further flame
spread. This feature may allow the TPO roofing membrane to easily
pass standard roof membrane flame tests. The resulting TPO membrane
blended with the acrylate additive may be stronger and more fire
resistant than conventional TPO membranes.
[0047] According to one embodiment, one or more of the roofing
membranes 104a-c of roofing system 100 of FIG. 1 may include the
acrylate additive described herein. In one embodiment, all of the
roofing membranes 104a-c include the acrylate additive and are
coupled together at overlapping portions. In another embodiment,
one or more of the roofing membranes 104a-c do not include the
acrylate additive, but are heat welded at overlapping portions with
an adjacent roofing membrane 104a-c that does include the acrylate
additive, such as when one or more membranes are being
replaced.
[0048] Referring now to FIG. 5A, illustrated is a roofing membrane
laminate 500 having a core 502 and a cap 504. The core 502 and cap
504 layers are typically between about 45 and 85 mils thick and are
bonded together, typically by laying the cap atop the core and
pressing the layers together while applying heat. The core 502 is
usually a conventional or lower grade roofing membrane, such as a
conventional or lower grade TPO membrane and may be made of
recycled polymers or include various fillers. The cap 504 of
laminate 500 is a higher quality TPO material having the acrylate
additive described herein. The laminate 500 is applied atop a roof
so that the cap 504 faces outward and is exposed to the
environment. The cap 504 provides the lower friction surface as
described herein so that the color and/or functionality of the
roofing membrane is maintained over a substantial portion of the
life of the membrane. In some embodiments, the overall cost of the
membrane may be reduced by bonding the higher quality cap 504 with
the lower quality core 502.
[0049] Referring now to FIG. 5B, illustrated is another roofing
membrane laminate 500' having a first core layer 502', a second
core layer 504', and a film layer 506'. The first core 502' and
second core 504' layers are typically between about 45 and 85 mils
thick and are bonded together as described previously. The film
layer 506', is typically about 10 mils thick and may likewise be
bonding atop second core layer 504'. The first core layer 502' and
second core layer 504' are usually conventional or lower grade
roofing membranes, such as conventional or lower grade TPO
membranes and may be made of recycled polymers or include various
fillers. The film layer 506' is a higher quality TPO or roofing
material having the acrylate additive described herein. The
laminate 500' is applied atop a roof so that the film layer 506'
faces outward and is exposed to the environment. The film layer
506' provides the lower friction surface as described herein so
that the color and/or functionality of the roofing membrane is
maintained over a substantial portion of the life of the membrane.
As described previously, using the film layer 506' may reduce the
overall cost of the roofing membrane.
[0050] Although not shown, in some embodiments, the roofing
membrane includes a single layer that includes the acrylate
additive and functional properties described herein. The single
layer may range in some embodiments between 45 and 160 mils thick.
Using a single layer may eliminate a processing step by removing
the requirement to couple two or more layers together.
[0051] Referring now to FIG. 3, illustrated is a method 300 of
making a roofing membrane. At block 310, a thermoplastic material
is provided. According to one embodiment, the thermoplastic
material is olefin or polyolefin so that the resulting roofing
membrane is a TPO membrane. At block 320, an acrylate additive is
blended with the thermoplastic material. The acrylate additive may
be blended with the thermoplastic material so as to comprise 10% by
weight or less of the blended material, 5% by weight or less of the
blended material, or in some embodiments, 3% by weight or less of
the blended material. As described herein, the acrylate additive
may include an ethylene chain and an acryloyl or acrylate group
bonded therewith. At block 330, the blended material is formed into
a substantially flat sheet, such as by extruding the blended
material through a die. The acrylate additive may migrate toward a
major surface of the blended material as the material is being
extruded through the die so that the resulting roofing membrane
includes a layer or coating of the acrylate additive on its
surface.
[0052] White pigment, such as Titanium Dioxide (TiO2), or another
color, may also be blended with the thermoplastic material to give
the resulting roofing membrane a desired color and/or other
functional properties, such as heat reflectance. The white pigment
may be blended with the roofing membrane material (e.g., TPO) so as
to comprise between about 2-6%, and more commonly about 3-5%, of
the roofing membrane. In some embodiments, the acrylate additive
may also include a maleic anhydride bonded with the ethylene chain.
In such embodiments, the method may further include blending a fire
retardant with the thermoplastic material. The fire retardant may
bond with the maleic anhydride as described herein. The maleic
anhydride may also bond with the TiO2 pigment and help diffuse and
disperse the TiO2 pigment throughout the roofing membrane.
[0053] The method may further include coupling the roofing membrane
with a roof surface. Similarly, the roofing membrane may be coupled
with additional roofing membranes atop the roof surface. For
example, the method may additionally include overlaying a portion
of the roofing membrane with an additional roofing membrane and
heat welding the two roofing membranes together. Heat welding of
the adjacent roofing membranes may be improved or enhanced by the
acrylate additive. The additional roofing membrane may or may not
have an acrylate additive. The coupled roofing membranes may form a
roofing system that has improved radiation reflecting properties,
improved color or aesthetic appeal, improved membrane strength,
improved weathering resistance, improved fire resistance, improved
weldability, and the like.
[0054] Having described several embodiments, it will be recognized
by those of skill in the art that various modifications,
alternative constructions, and equivalents may be used without
departing from the spirit of the invention. Additionally, a number
of well-known processes and elements have not been described in
order to avoid unnecessarily obscuring the present invention.
Accordingly, the above description should not be taken as limiting
the scope of the invention.
[0055] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower limit
unless the context clearly dictates otherwise, between the upper
and lower limits of that range is also specifically disclosed. Each
smaller range between any stated value or intervening value in a
stated range and any other stated or intervening value in that
stated range is encompassed. The upper and lower limits of these
smaller ranges may independently be included or excluded in the
range, and each range where either, neither or both limits are
included in the smaller ranges is also encompassed within the
invention, subject to any specifically excluded limit in the stated
range. Where the stated range includes one or both of the limits,
ranges excluding either or both of those included limits are also
included.
[0056] As used herein and in the appended claims, the singular
forms "a", "an", and "the" include plural referents unless the
context clearly dictates otherwise. Thus, for example, reference to
"a process" includes a plurality of such processes and reference to
"the device" includes reference to one or more devices and
equivalents thereof known to those skilled in the art, and so
forth.
[0057] Also, the words "comprise," "comprising," "include,"
"including," and "includes" when used in this specification and in
the following claims are intended to specify the presence of stated
features, integers, components, or steps, but they do not preclude
the presence or addition of one or more other features, integers,
components, steps, acts, or groups.
* * * * *